Starches and starch fractions. Part I. The determination of dextrose and maltose by the ferri‐cyanide‐carbonate reagent, with special reference to the effect of inorganic salts

1947

1x7 which had to be taken was to discontinue the addition of bromine if, for some reason or other, the stirrer failed to work. (Accumulation of free bromine in the vessel is dangerous as it might react suddenly with great violence,)The mixture of sulphuric acid and hydrobromic acids was converted into calcium bromide by neutralisation with slaked lime.The solution of calcium bromide obtained was evaporated until a concentration of about 75y0 was reached. Such a solution solidifies on cooling. A typical analysis of the final product was as follows :CaBr, 76y0b.w. ; CaO 0.039y0 ; Fe 0 . 0 1 3~~ ; S", SO.,, BrO', absent; Chloride ion 0.3% (calculated as calcium chloride).The product was used for the manufacture of bromine salts for pharmaceutical purposes. SummaryDuring the war, large quantities of calcium bromide were produced at the Dead Sea works of Palestine Potash Ltd. from hydrobromic acid obtained through the reduction of bromine by means of sulphur.The reaction between bromine, sulphur and water is strongly exothermic ; at low temperatures its rate is slow and it cannot be brought to completion owing to inhibition by the reaction products. At temperatures above 70' this inhibition effect disappears and the rate of reaction increases considerably. The industrial process here described was carried out at the boiling point of the reaction mixture. The problem of dissipating the heat evolved in the reaction was solved by bringing the vapours of the boiling mixture into contact with the ice. The condensed vapours and the water formed by the melting of the ice were allowed to flow back into the reaction vessel. This procedure allows the use of a reaction vessel made of a material of low heat conductivity, but resistant to corrosion. to commemorate the 70th anNvcrsary of Dr. Chaim Weizmann, Rchoboth, Palestine Bloch, H., Goldschmidt, P, Littman, H., Palestine Pat. No. 1618 I. Failure to determine the 1-2% of non-carbohydrate constituents present.2. The use of methods not giving complete drying for the determination of the moisture content.3. The use of insufficiently accurate methods for the detcrmination of the dextrose produced. 4. Failure to allow for any decomposition of the dextrose produced. 5. Incomplete hydrolysis of the starch. The starch sitbstrute.-The starch used in the present investigation was a lintnerised wheat starch prepared by treating B.D.H.:wheat starch with 2 I N-hydrochloric acid (250 g. starch * Specified as zoo ml.:of starch suspension and 20 ml. HCl of sp.gr.

Starches and starch fractions. Part II. The determination of starch by hydrolysis with hydrochloric acid

Lampitt¹,

Fuller²,

1947

Starches and starch fractions. Part III. The intensity of the colour of starch‐iodine‐iodide solutions as an index of the amylose‐amylo‐pectin ratio

Lampitt¹,

Fuller²,

1947

The quantitative determination of the % of amylose and amylo‐pectin in starches and starch fractions is best carried out using a low starch: iodine ratio. The use of a high starch: iodine ratio is undesirable, since it may not reveal differences in the amylose : amylo‐pectin ratio, but, even under these unfavourable conditions, any significant differences in colour intensity are still indicative of differences in the amylose : amylopectin ratio.

The fractionation of potato starch part II. The reducing powers, mean molecular weights and solubilities of the fractions

Lampitt¹,

Fuller²,

1948

The reducing powers of the fractions from ground potato starch and the mean molecular weights calculated from them show that, as in the case of wheat starch, grinding in a ball mill causes vcry considcmblc depolymcrization.This process takes place more rapidly with potato starch than with wheat starch. In contrast to wheat starch, the differences in solubility between the dricd potato starch fractions arc cxplainablc by the differences in the mean molecular weights of the fractions.Since the publication of the series of papers on wheat starch,'-!' more evidence has been obtained by other workers that grinding in a ball mill depolymerizes substances of high molecular weight (mike starchlo ; cellulose~~~ 1% 13 ; polystyrene" and polyosymethylene"). Hess and his co-workers". l2, 1& lG have concluded that depolymxization by this means is due not to hydrolysis, oxidation or thermal decomposition, but to the stresses and strains set up in the mxcromolecules of the polymer under the impact of the cascading balls ; under such conditions, the macromolecules disintegrate. That purely physical stresses can cause depolymerization has also been observed in the action of ultrasonic waves on starches17p and other 2oThe structural formulae of both the amylose and amylopecth fractions of the common starches indicate that each molecule is terminated at one end by an aldehydic reducing group.21. ?% 23 That the reducing power is inversely proportional to the molecular weight (or to properties that depend thereon) has been demsnstrated for starches in many cases", 25* 27 and has been quantitatively verified for starch,?& dextrins,-"0,30. 31. 39, 33, 34 The present paper deals with (a) the reducing powers and tht mean molecular weights of a number of fractions derived from potato starch ground in a ball mill for various times and also from the unground starch and (b) the solubilities of the dried fractions.